The inventive subject matter relates to power supply apparatus and methods, more particularly, to AC/DC converter apparatus and systems and methods employing the same.
In many applications, DC power distribution systems offer several potential advantages over AC power distribution systems. For example, HVDC transmission lines are sometimes used for long distance power transmission applications because DC lines generally have lower losses from line capacitance and skin effect. HVDC lines may also be used to interconnect unsynchronized AC systems. In undersea applications, DC transmission systems may have lower losses in transferring power from power sources that are far removed from subsea loads. Medium voltage DC power systems are also finding increased use in shipboard power distribution, where DC power distribution lines may be an extension of DC links of electric propulsion and thruster drives, and can facilitate connection of batteries and other storage devices. Converters used in a DC power distribution system can provide means to further optimize efficiency by providing greater control of power flows. DC power distribution systems are often fed by power converters that are used to interface the DC system to an AC source, such as a generator or AC power grid.
Current source rectifiers (CSRs) are may be used to generate a DC output from an AC source. A CSR is a single-stage converter whose DC output can be current limited by proper control of switching transistors of the current source rectifier. An example of an application of CSR to an uninterruptible power supply is described in United States Patent Application Publication No. 2015/0171663 entitled “UNINTERRUPTIBLE POWER SYSTEMS USING SOURCE RECTIFIERS AND METHODS OF OPERATING THE SAME”, incorporated by reference herein in its entirety. Another example of the use of current source rectifiers is provided in a paper entitled “Implementation of Sine-Wave Input/Output BLDC Inverter for Low Inductance Shipboard PM Motor Drives using Modular Power Platform”, Kranz et al., IEEE Electric Ship Technologies Forum (2011) pp. 46-51.